Ink reservoir



March 1, 1966 c. A. SONNTAG- INK RESERVOIR Filed Nov. 17, 1960 HIE nvwzzvrm CLEMENS A. SONNTAG FHPE 5- United States Patent C 3,237,606 INK RESERVOIR Clemens A. Sonntag, Janesville, Wis., assignor to The Parker Pen Company, Janesville, Wis., a corporation of Wisconsin Filed Nov. 17, 1960, Ser. No. 70,058 11 Claims. (Cl. 12045.4)

The present invention generally relates to ink reservoirs of the type used in fountain pens and it more particularly relates to means for preventing fluid ink from being held within the closed upper end of an ink reservoir instead of falling by gravity to the bottom of the reservoir wherein it can be controllably fed to the writing point.

Ink reservoirs for fountain pens are normally tubular and of relatively small cross sectional area which can and frequently does cause ink to hang up in the necessarily closed upper end of the reservoir. This tendency of the ink to be held in the upper closed end of the pen even when the pen is held in a writing position starves the nib of the pen giving the impression to the user that the reservoir is empty when in reality it may contain a substantial quantity of ink. In the past, one attempt to alleviate this condition utilized a horsehair disposed within the reservoir for the purpose of breaking the meniscus at the bottom end of the ink which is trapped in the closed end of the reservoir. Another attempt to solve this problem employed a small ball or other particle loosely disposed in the reservoir.

Although fountain pens having reservoirs of the refillable type may exhibit this condition, the problem has not been a serious one with the refillable reservoirs for at least two reasons. In the first place, since such reservoirs can be readily refilled, the problem is little more than a nuisance. In the second place, the materials from which refillable type reservoirs are formed, while initially non-wettable to a suflicient degree to support a quantity of ink in the closed end of the reservoir, tend to become increasingly wettable with continued filling and refilling so that if the problem exists at all, the condition corrects itself Within a short time after the pen is in use.

At the present time, however, replaceable or throwaway types of ink cartridges are extremely popular because of the speed and facility with which the ink supply of the associated fountain pen can'be replenished. However, since such cartridges are not normally reused, their inner surfaces do not change from their normal nonwettable characteristics as do refillable type reservoirs, and, therefore, the problem of hang up is always present. Moreover, any ink remaining in the closed end of a spent cartridge cannot later be used and, therefore, is wasted. When it is realized that the amount of ink which is frequently held by capillary action or other forces in the closed end of an ink cartridge is perhaps a quarter or more of the ink contained in a filled reservoir, the amount of ink wasted and the cost thereof becomes substantial. Moreover, an important advantage of an ink cartridge of the throw-away type is that it holds an extremely large quantity of ink and, moreover, minimizes the time lost in refilling the pen. Such advantages are, moreover, offset if the cartridge must be replaced before all of the ink in the cartridge has been used up or at best if the user must make some effort to dislodge the ink from the lower end of the cartridge after he had disassembled the pen to discover that all of the ink has not been used.

Therefore, a principal object of the present invention is to provide a new and improved ink reservoir for preventing ink from being held in the closed end thereof against the force of gravity.

Another object of the present invention is to provide "ice a new and improved throw-away type of ink cartridge which is so constructed as to eliminate the problem of ink hang up in the closed end of the cartridge.

A further object of the present invention is to provide an ink reservoir employing means which do not appreciably increase the manufacturing cost of the reservoir while preventing ink from being held against the force of gravity in the upper closed end of the reservoir.

Briefly, the above and further objects are realized in accordance with the present invention by providing an ink reservoir having provided in the wall thereof a groove of capillary dimension extending from the closed end of the reservoir to a location substantially remote therefrom and while preferably extends to a location in proximity to the opposite end of the reservoir.

Further objects and advantages and a better understanding of the present invention may be had by reference to the following detailed description taken in connection with the accompanying drawing in which:

FIG. 1 is a longitudinally sectioned view of a throwaway type of ink reservoir embodying the present invention; and

FIG. 2 is a cross-sectional view taken along the line 22 in FIG. 1 assuming the entire reservoir to be shown in FIG. 1.

Referring now to the drawing, there is shown a throwaway type of ink reservoir or cartridge 10 consisting of a generally tubular shell 12 and a plug 13' which has a tubular portion 14 which is fitted into one end of the shell 12 and sealed thereto by any suitable means such, for example, as by cementing or welding. The plug 13 further includes a generally annular flange 15 which abuts against the end 16 of the shell 12 to facilitate assembly of the cartridge 10 and to insure a hermetically tight seal between the plug 13 and the shell 12. An integral wall 17 is provided within the plug 13 to hold ink in the cartridge 10 prior to its insertion in an associated fountain pen. When the cartridge is placed in the associated fountain pen, the wall 17 is partially severed from the plug and shifted to one side to permit the passage of ink through the plug and into the feed mechanism of the pen. A structure which is suitable for this purpose is described in a copending application Serial No. 74,304, filed December 7, 1960 by Homer Theodore Green and assigned to the same assignee as the present invention now Patent No. 3,134,362.

The shell 12 has an outer envelope formed to closely follow the contour of the barrel of the pen in which it is adapted to be used and, therefore, the shell 12 tapers towards the top or right-hand end as viewed in FIG. 1. Since a desirable feature of any ink reservoir and particularly a replaceable type of cartridge is its ability to store large quantities of ink, it is desirable that the cartridge 12 be sufiiciently long to extend as far as possible into the barrel of the associated pen and because of the desirability of tapering the barrel of a fountain pen for aesthetic and other reasons it necessarily follows that the upper end of the cartridge, the right-handend as viewed in FIG. 1, is relatively narrow in cross-sectional area.

As is well known in the art, the right-hand end of the cartridge shell 12 must be sealed and for reason the shell 12 is provided with an integral end portion 20 which closes the upper end of the cartridge thereby to completely seal it from the atmosphere.

The cartridge 10 is designed for use with liquid inks which ordinarily have a surface tension of the order of 45 to 60 dynes per centimeter. Moreover, the shell 12 is preferably formed of a relatively rigid, at least partially transparent, and relatively inexpensive material. Polyethylene and particularly linear polyethylene is particularly suited for this purpose and in a commercial device embodying the present invention the shell 12 is molded of linear polyethylene. An inherent characteristic of linear polyethylene and most other materials which are suited for use in the shell 12 is that it is sufliciently non-Wettable by conventional writing type fluid inks to support a quantity of ink in the closed end of the reservoir. Therefore, the relatively small diameter of the cartridge, particularly in the vicinity of the closed end of the shell 12 together with the non-wettability characteristic of the inner surface of the shell 12 and the surface tension of the ink provided a meniscus when the reservoir is moved to an upright position, from a horizontal position in which the ink had flowed into the closed end. This meniscus exerts a suflicient force to counteract that exerted on the ink by gravity thereby to hold a substantial quantity of ink in the closed end of the shell 12.

In order to prevent the ink from thus remaining in the closed end of the tube, there is provided in accordance with the present invention two pairs of longitudinally extending ribs 21, 22 and 23, 24. The ribs 2124 are integral with the shell 12 and are preferably molded when the shell 12 is formed. The ribs 2124 extend from the closed end 20 of the shell 12 to a location in proximity to the opposite end of the shell 1.2 and thus terminate near the plug 13. The ribs 21 and 22 are sufficiently close together that the cross-sectional area of the channel formed between each pair of ribs is of capillary dimension to provide a capillary passage from the upper end of the shell 12 to a location near the bottom thereof. Consequently, when a meniscus forms in the ink supply chamber at the upper end of the shell 12 thereby to hold ink in the upper closed end of the reservoir, that ink which is thus hung up is attracted by capillary action into the capillary grooves provided between the associated ribs and also between each of the ribs and the adjacent portion of the inner surface of the shell 12 and fed by such capillary passages to the bottom of the reservoir. The ribs 21 and 22 thus provide capillary passageways which drain the ink from the closed end of the cartridge.

Although a single pair of ribs such, for example, as the ribs 21 and 22 will provide the necessary action to drain the ink from the closed end, it is desirable to provide the additional pair of ribs 23 and 24 to prevent any mechanical unbalance of the stresses in the shell 12 since such stresses would tend to warp or otherwise deform the reservoir 12.

While various dimensions and materials may be used to carry out the present invention, the teachings of the present invention may be successfully carried out in a device having the following dimensions:

Length of shell 12 2.8 inches. Maximum internal diameter of shell 12 .24 inch. Minimum diameter of shell 12 .154 inch.

Distance between groves 21 and 22 .010 inch. Distance between grooves 23 and 24 .010 inch. Material of shell 12 linear polyethylene.

Although it might be desirable under certain conditions to extend the ribs 2124 to the very bottom of the reservoir, in order to facilitate the providing of a good seal between the plug 13 and the shell 12 it is desirable to terminate the ribs 21 and 22 at a location remote from the adjoining surface of the plug 13 and the shell 12. If the capillary grooves were to connect with the adjoining surface of the plug 13 and the shell 12, it would be extremely difficult to provide a hermetically tight seal between the plug 13 and the shell 12 because of the tendency of ink to flow into the seal area. Inasmuch as the downward force exerted by the ink contained in the capillary passageways between the closed end of the reservoir and the point at which the ribs 21-24 terminate produces a sufiicient force to cause ink to drain from the bottom of the capillary channels, the necessity of extending the capillary grooves the last small fraction of an inch to the plug does not appreciably affect the operability of the reservoir 10.

Another way in which capillary forces may be used to drain ink from the closed end of the reservoir is to provide a textured internal surface on the cartridge, which surface provides tiny interconnected passageways of capillary dimensions interconnecting the two ends of the cartridge.

While the present invention has been described in connection with a particular embodiment thereof, it will be understood that those skilled in the art may make many changes and modifications without departing from the true spirit and scope of the invention which invention is intended to be coveredby the following claims which are appended to and form a part of the present specification.

I claim:

1. An ink reservoir for holding a supply of fluid ink for a fountain pen, comprising an elongated tubular body having an inner wall defining a relatively narrow elongated substantially unobstructed ink supply chamber closed at one end, said body being formed of a material substantially non-wettable by said ink and said chamber having a cross-sectional area relative to the surface tension of said ink which would enable a quantity of said ink to be held in said closed end portion of said chamber when said body is in .a vertical position with said closed end at the top, and a groove in the inner wall of said body opening into said chamber, said groove having a cross-sectional area of capillary dimension and extending from said closed end of said chamber to a location in said chamber sufficiently remote from said closed end that the downward force exerted by the ink in the groove between said location and said closed end exceeds the forces tending to hold said ink in said closed end, whereby ink may feed out of said closed end of said chamber via said capillary groove and ink is thereby prevented from being held in said closed end of said chamber by capillary action.

2. An ink reservoir as set forth in claim 1 wherein said tubular body is a throw-away type of ink cartridge and said groove is formed therein by a longitudinal rib extending from said closed end of said chamber to a location proximately disposed with the opposite end of said chamber.

3. An ink reservoir as set forth in claim 1 wherein said tubular body includes a pair of longitudinally extending ribs spaced apart to define said capillary groove between said ribs.

4. An ink reservoir as set forth in claim 3 comprising an additional pair of longitudinally extending ribs provided on the inner wall of said body at a location diametrically opposite to the location of the first said pair of ribs.

5. An ink reservoir as set forth in claim 4 wherein said cartridge is formed of linear polyethylene.

6. An ink reservoir for holding a supply of fluid ink for a fountain pen, comprising an elongated and tapered tubular body having an inner wall defining a relatively narrow elongated substantially unobstructed ink supply chamber therein integrally closed at one end, said body being open at the other end, a plug fitted into said open end of said body opposite to said integrally closed end of said body, and a capillary groove extending along the inner wall of said body from said closed end of said chamber to a location in proximity to but displaced from said plug.

7. An ink reservoir for holding a supply of fluid ink for a fountain pen, comprising anelongated tubular body having an inner wall defining a relatively narrow elongated substantially unobstructed ink supply chamber closed at one end, said body being formed of a material substantially non-wettable by said ink and said chamber having a cross-sectional area relative to the surface tension of said ink which would enable a quan tity of said ink to be held in said closed end portion of said chamber when said body is in a vertical position 

9. AN INK RESERVOIR FOR HOLDING A SUPPLY OF INK FOR A PEN HAVING A WRITING ELEMENT, SAID RESERVOIR COMPRISING A ELONGATED TUBULAR BODY HAVING AN INNER WALL DEFINING A RELATIVELY NARROW SUBSTANTIALLY UNOBSTRUCTED INK SUPPLY CHAMBER THEREIN, SAID BODY BEING CLOSED AT ONE END REMOTE FROM THE END THEREOF FROM WHICH INK IS ADAPTED TO BE FED TO THE WRITING ELEMENT OF SAID PEN, SAID BODY BEING PROVIDED ON THE INTERNAL CHAMBER DEFINING WALL THEREOF WITH A LONGITUDINAL EXTENDING CAPILLARY GROOVES FOR FEEDING INK TOWARD THE END OF SAID CHAMBER FROM WHICH INK IS FED TO SAID WRITING ELEMENT. 